Lifting tongs for handling heavy products

ABSTRACT

Lifting tongs for handling heavy rigid loads such as coils of sheet metal comprise two gripping arms each provided with a lug for supporting said load and a suspension member with two pivots on which are articulated two pairs of arms crossed in scissors fashion articulated to said gripping arms so that the tongs may be pivoted in relation to said suspension member, by an angle of at least a few degrees, between certain limits determined by stops.

United States Patent [72] inventor Ghislain Antoine Jean-Marie Martelee Liege, Belgium [21] Appl. No. 724,816

[22] Filed Apr. 29, 1968 [45] Patented June 1, 1971 [73] Assignee Cockerill-Ougree-Providence et Esperance- Longdoz en abregeC0ckeri1l Seraing-lez-Liege, Belgium [32] Priority May 31, 1967 [33] Belgium [54] LIFTING TONGS FOR HANDLING HEAVY PRODUCTS 5 Claims, 2 Drawing Figs.

[52] U.S. Cl 294/115, 294/ 1 18 [51] Int. Cl B66c 1/28,

[50] Field of Search l06,67,78,110,ll8,1l3,119

[56] References Cited UNITED STATES PATENTS 2,857,193 10/1958 Heppenstall 294/106X 3,469,879 9/1969 Tezuka i 294/106 2,610,890 9/1952 .iaeger 294/110 3,401,974 9/1968 Martelee 294/110 1,451,185 4/1923 Staggers 294/118 FOREIGN PATENTS 747,526 4/1956 Great Britain 294/113 805,615 12/1958 Great Britain.. 294/119 18,085 1/1908 Norway 294/106 Primary Examiner-Harvey C. Hornsby Assistant Examiner-W. Scott Carson AltorneySughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT: Lifting tongs for handling heavy rigid loads such as coils of sheet metal comprise two gripping arms each provided with a lug for supporting said load and a suspension member with two pivots on which are articulated two pairs of arms crossed in scissors fashion articulated to said gripping arms so that the tongs may be pivoted in relation to said suspension member, by an angle of at least a few degrees, between certain limits determined by stops.

LIFTING TONGS FOR HANDLING HEAVY PRODUCTS This invention relates to lifting tongs for handling heavy rigid loads such, for example, as coiled metal sheets.

For handling heavy rigid loads and, in particular, coils or bundles of metal sheets, it is known to utilize lifting tongs so arranged that the gripping arms remain parallel to one another as they are brought-together or drawn apart in order to seize the heavy rigid load in question. Further, the said lifting tongs are sometimes provided with a device permitting them to be pivoted round the axis defined by the intersection of the plane determined by the axes of the said gripping arms on the one hand and the plane extending perpendicularly to this plane midway between these two gripping arms on the other hand and which in what follows will be termed the center plane of the tongs.

From the nature of their design these known lifting tongs are provided with a suspension member which frequently consists of a rigid metal rod. in certain known cases this rod is replaced by a complex device comprising a part of the locking mechanism of the said gripping arms and of the mechanism for pivoting the tongsround the axis defined above. ln these known tongs the said suspension member is maintained in position relatively to the remaining part of the tongs, due to mechanism controlling the action of the tongs. The axis of this suspension member coincides with the pivotal axis defined above.

When it is a question of lifting, by means of such tongs, a heavy rigid load, the said load only begins to leave the surface on which it is resting when the said two fingers of the tongs have simultaneously gripped the said load at two grip points. it frequently happens that at this moment the said center plane of the tongs is inclined to the vertical if the said two grip points are not strictly at the same level. The result is that at the moment when lifting is commenced, the said heavy load begins to leave its supporting surface, the center of gravity of the tongs load assembly is not on the axis of lifting force being exerted on the tongs.',The tongs-load assembly pivots round one or more points of contact of the load with its supporting surface until the center of gravity of the said assembly has been brought back onto said lifting axis. As a result a lateral force is exerted on the said load by one of the two gripping arms of the tongs which is nearest to the said axis of lifting force. Other things being'equal, the magnitude of this lateral force is in direct proportion to the distance of the said axis from the center of gravity of the tongs-load assembly. The deleterious effect of this lateral force is particularly felt in the case where the product to be lifted is a coil of fine metal sheets, because there is a risk of crushing the edges of the windings of the said coil.

Furthermore,v because of the inclination of the tongs, the said tractive force axis is not directed along the axis of the suspension member of the tongs. The result is that this latter is subjected to considerable bending stresses frequently giving rise to risk of damage to the suspension member itself and also to the mechanisms controlling the working of the tongs.

According to the invention there is provided lifting tongs for handling heavy rigid loads, such as, for example, ls of sheet metal comprising two gripping arms each provided with a lug designed to support the said heavy rigid loads, the said tongs being provided with a suspension member adapted to be coupled to a lifting device, wherein the suspension member being pivoted, in relation to the remaining portion of the tongs, on an axis perpendicular to the plane determined by the axes of the said two gripping arms and maintained between certain limits of angular rotation by stops fixed to the remainder of the tongs, the said stops being such that they permit the said suspension member to move away, in relation to the center plane of the tongs, by an angle of at least a few degrees.

If in the course of lifting a rigid heavy load with tongs in accordance with the invention the said tongs are set askew, the tongs suspension member will pivot round the said perpendicular axis in such a way as to bring the tractive force being exerted on the tongs into coincidence with said axis. Consequently the said axis approaches the center of gravity of the tongs and this in direct proportion to the closeness of the said perpendicular axis to the said gripping arms of the tongs. Other things being equal, the lateral force mentioned above is therefore considerably less for the tongs in accordance with the invention than for conventional tongs.

Further, in the tongs in accordance with the invention, the bending stresses on the suspension member are reduced, because this member is positioned in the line of the tractive force being exerted on the tongs.

Specific embodiments of the invention will now be described by way of example, with reference to the attached drawings, in which:

FIG. 1 is a diagrammatic view in elevation of one embodiment of the tongs in accordance with the invention,

FIG. 2 is a partly broken away diagrammatic view in perspective of part of a spring box forming a further embodiment of the tongs in accordance with the invention.

Throughout the figures like parts are designated by like reference numerals.

The tongs shown in FIG. 1 comprise two gripping arms 1 and 2 each provided with lugs 3 and 4 respectively, designed to support a heavy rigid load such as 5. These two gripping arms 1 and 2 extend upwardly to form two guides 6 and 7 pierced respectively by a slot 8 and a slot 9. The two gripping arms 1 and 2 are articulated to the ends of two pairs of arms and links, that is to say the arm 10 and link 11, articulated round a pivot 12, and the arm 13 and link 14, articulated round a pivot 15, respectively.

The links 11 and 14 are each articulated at their remote ends to the gripping arms 1 and 2 respectively on pivots 16 and 17. The other ends ofthese links 11 and 14 are articulated on a common pivot 18.

The arms 10 and 13 are mutually articulated at one of their ends on a pivot 19. The other ends of the arms 10 and 13 are each provided with a lug, 20 and 21 for sliding engagement in slots 8 and 9 respectively. To the arm 10 is attached a rod 22 on which there acts ajack 23 by means of which the gripping arms 1 and 2, articulated to the arms and links 10,11,13 and 14, are caused to move apart or closer.

To the pivot 19 is also attached a rod 24 forming part of the tongs suspension member and designed to engage a hook 25 of a lifting device. This suspension rod 24 can pivot around the axis of the said pivot 19, perpendicularly to the plane defined by the axes of the gripping arms 1 and 2.

To the pivot 18 is also fixed a box 26 provided with two laminated springs 27 and 28 fixed rigidly to the boy 26, and which are pretensioned, that is to say they already exert equal and opposite forces on the rod 24 when the said rod is vertical. These springs 27 and 28 act in opposition on the rod 24 is such a way as to tend to bring the rod 24 towards the center plane of the tongs, when the said rod 24 has pivoted round the axis of the pivot 19. When the said springs 27 and 28 are under maximum compression against the walls of the box 26, they constitute stops fixed to the remainder of the tongs.

in an advantageous form of embodiment of the tongs in accordance with the invention, part of which is shown diagrammatically in FIG. 2, the suspension rod 24 is bifurcated about the pivot 18 to provide two parallel rods 29 and 30 which pass on either side of the pivot 18 and whose axes define a plane perpendicular to the plane defined by the axes of the gripping arms 1 and 2. To the ends of the pivot 18 are fixed two identical boxes 31 and 32 through which pass the rods 29 and 30 respectively.

Each of these two boxes 31 and 32 are provided with two laminated springs, that is to say 33 and 34, and 35 and 36, respectively. The springs 33 and 34 are fixed rigidly to the box 31 while the springs 35 and 36 are fixed rigidly to the box 32. The springs 33,34 act in opposition on the rod 29 and the springs 35,36 act similarly on the rod 30, tending to bring the rods 24,29 and 30 simultaneously towards the center plane of the tongs, when the rod 24 has pivoted by an angle of at least a few degrees round the axis of the pivot 19.

When the axes of the rods 24,29 and 30 are located in the said center plane, the springs 33 and 34, on the one hand, and 35 and 36 on the other hand, are held at a certain distance from the rods 29 and 30 respectively, by means of stops 37 and 38, fixed to the boxes 31 and 32.

The springs 33,34 and 35,36 are preloaded and press on the stop pieces such as 37 and 38. Thus wear on the rods 29 and 30 is minimized and the tongs are always returned to the vertical in spite of the friction of the pivot 18 in respect of the suspension rod.

This invention is not restricted to the forms of embodiment described above, but numerous modifications may be made in What I claim is:

l. Lifting tongs for handling a heavy rigid load such as a coii of sheet metal,- comprising two parallel movable gripping arms, a lug on each of said gripping arms for supporting said heavy rigid load, a suspension member for engaging a hook of a lifting device, a lower pivot on said suspension member, two arms connected between said lower pivot and said gripping arms, an upper pivot on said suspension member, two links connected between said arms and said upper pivot, a box carried on said upper pivot; biasing means in said box on both sides of said suspension member so that said gripping arms are pivotally movable on said lower pivot relative to said suspen sion member, said biasing means acting in opposition on said suspension member to normally maintain said suspension member in a neutral position between said biasing means, and stop means in said box on both sides of said suspension member for limiting said pivoting movement to an angle of approximately a few degrees.

2. Lifting tongs as claimed in claim 1 wherein said biasing means are springs.

3. Lifting tongs as claimed in claim 2 wherein said springs are prestressed in order to return said suspension member to said neutral position.

4. Lifting tongs as claimed in claim 1 wherein said step means are shoulders projecting in said box.

5. Lifting tongs as claimed in claim 1 wherein said suspension member is a rod carrying said lower pivot at its lower end. 

1. Lifting tongs for handling a heavy rigid load such as a coil of sheet metal, comprising two parallel movable gripping arms, a lug on each of said gripping arms for supporting said heavy rigid load, a suspension member for engaging a hook of a lifting device, a lower pivot on said suspension member, two arms connected between said lower pivot and said gripping arms, an upper pivot on said suspension member, two links connected between said arms and said upper pivot, a box carried on said upper pivot; biasing means in said box on both sides of said suspension member so that said gripping arms are pivotally movable on said lower pivot relative to said suspension member, said biasing means acting in opposition on said suspension member to normally maintain said suspension member in a neutral position between said biasing means, and stop means in said box on both sides of said suspension member for limiting said pivoting movement to an angle of approximately a few degrees.
 2. Lifting tongs as claimed in claim 1 wherein said biasing means are springs.
 3. Lifting tongs as claimed in claim 2 wherein said springs are prestressed in order to return said suspension member to said neutral position.
 4. Lifting tongs as claimed in claim 1 wherein said stop means are shoulders projecting in said box.
 5. Lifting tongs as claimed in claim 1 wherein said suspension member is a rod carrying said lower pivot at its lower end. 